'Smoking Gun' Reveals How the Inflationary Big Bang Happened

byAlan Boyle

The 10-meter South Pole Telescope and the BICEP (Background Imaging of Cosmic Extragalactic Polarization) Telescope are silhouetted against the Milky Way. BICEP2 recently detected gravitational waves in the cosmic microwave background, a discovery that supports the cosmic inflation theory of how the universe began.Keith Vanderlinde / NSF

New findings show that the universe underwent a burst of inflation that was seemingly faster than the speed of light in the first instant of its existence, throwing off a storm of exotic gravitational waves in the process.

The evidence comes from the BICEP2 experiment at the South Pole, which captures and analyzes the faint glow left over from the Big Bang. BICEP2's researchers found a subtle twisty pattern in the polarization of that light, which would be characteristic of primordial gravitational waves.

The results support a concept known as inflationary Big Bang theory, and they can be further analyzed to reconstruct how the Big Bang blew up 13.8 billion years ago. Even in advance of Monday's public reveal, physicists were gushing over the implications.

"Other than finding life on other planets or directly detecting dark matter, I can't think of any other plausible near-term astrophysical discovery more important than this one for improving our understanding of the universe," Caltech theoretical physicist Sean Carroll said in a pre-announcement blog posting.

MIT cosmologist Max Tegmark wrote that "before long, it will lead to at least one Nobel Prize."

For decades, Guth, Linde and other theorists have advanced the view that the universe somehow inflated itself to huge size in as little as an undecillionth of a second (10 to the negative 36th power). If such an expansion were measured as a three-dimensional spatial phenomenon, the velocity would seem to exceed the speed of light. But in this case, the entire cosmos would have expanded into extradimensional space.

Inflationary Big Bang theory explains some of the strange twists in the data collected so far about the birth of the cosmos, but it poses challenges as well. BICEP2, which stands for Background Imaging of Cosmic Extragalactic Polarization 2, provides the data to address those challenges.

BICEP2's detectors were built to look for patterns of polarization in the cosmic microwave background radiation, the glow left over from the Big Bang. A characteristic pattern known as the B-mode, which is twisted like a pinwheel, would point to the imprint of gravitational waves from the cosmic blow-up.

A map of temperature differences in the cosmic microwave background reveals characteristic pinwheel patterns in the polarization of light, which points to the imprint of primordial gravitational waves.BICEP2 Collaboration

Surprisingly strong signal

On Monday, researchers reported that they found a surprisingly strong pattern in the data after three years of analysis.

"This has been like looking for a needle in a haystack, but instead we found a crowbar," the University of Minnesota's Clem Pryke, a co-leader of the BICEP2 team, said in Monday's news release.

In geekspeak, the discovery translates to a value of 0.2 for r, with a margin of error of plus 0.07 or minus 0.05, at a confidence level exceeding 5 sigma.

That value for r is significantly higher than expected, which suggests that many of the previously proposed models for cosmic inflation can be ruled out. The best fit for the data is a model in which all the fundamental forces except for gravity — that is, electromagnetism as well as the weak and strong nuclear force — were unified as one super-force when the universe was born.

BICEP2's findings aren't the final word on the inflationary Big Bang: The conclusions could be strengthened — or questioned — when further results from the European Space Agency's Planck mission are released.

"This is not the end," Pryke told reporters Monday. "It's the beginning."

Update for 2:12 p.m. ET March 17: Here's what Arizona State University physicist Lawrence Krauss had to say about the BICEP2 findings in an email:

"This is hugely important, if true. It is an empirical window on the universe at almost the beginning of time. We will need to wait to see if it is confirmed of course, but if it is, it is the best hope of directly testing ideas about how the universe behaved 10^-35 sec after the big bang. As I have described before, these results are allowing us to not only address physical questions, but to turn previously metaphysical questions into scientific ones, such as 'Why is there something rather than nothing.'

"The results look very, very convincing. The experimenters were careful. They had to be. Not only does this result have tension with earlier claimed upper limits, but they knew the scrutiny on any such claim would be profound. They didn't want to screw up in front of the world."

"Talking to and listening to experts, I'd describe the mood as cautiously optimistic; some people are worried about certain weird features of the data, while others seem less concerned about them. ... typical when a new discovery is claimed. I'm disturbed that the media is declaring victory before the scientific community is ready to. That didn't happen with the Higgs discovery, where the media was, wisely, far more patient."